This invention relates to an electronically controlled solenoid device and more particularly to a method of determining the static armature position of the solenoid device without the use of sensors.
A conventional electromagnetic actuator for opening and closing a valve of an internal combustion engine generally includes a solenoid which, when energized, produces an electromagnetic force on an armature. The armature is biased by a return spring and the armature is coupled with a cylinder valve of the engine. The armature is held by the electromagnet in one operating position against a stator of the actuator and, by de-energizing the electromagnet, the armature may move towards and into another operating position by the return spring.
Conventional high speed electronic solenoid devices of the fuel injector type include an armature movable with respect to a stator to control movement of an injector valve.
In solenoid devices of either an electromagnetic actuator or a fuel injector type, it may be desirable to determine the static armature position relative to the stator for the purposes of mechanical adjustment or to determine the positional status of the armature for diagnostic purposes.
In an electromagnetic actuator, it is often required to space the armature a specific distance between the electromagnets (a mechanical center adjustment). Some conventional methods of the mechanical center adjustment are as follows:
1) During the actuator installation, the armature/stator gap is mechanically measured and necessary adjustments are made. Re-adjustment would require returning to nearly the installation stage of assembly to gain access for mechanical re-measurement or would require the use of a position sensor installed on the actuator.
2) While the actuator is operating, the landing velocity, in open loop control of the armature, is adjusted to be relatively the same on opening and closing, given identical input current profiles. The velocity measurement requires either a laser Doppler sensor or some other reasonably accurate velocity sensor, or position sensor whose signal derivative is used as a velocity.
3) While the actuator is operating, the current, in open loop control, is observed for any de-regulation of level during armature flight. The de-regulation is subjectively used to determine approximate armature offset from some optimal position.
Thus, there is a need to determine the static position of an armature of an electronically controlled solenoid device which does not require use of a sensor, does not require cycling operation of the device and provides for a repeatable set-point after installation.
An object of the present invention is to fulfill the need referred to above. In accordance with the principles of the present invention, this objective is obtained by providing a method of determining a static position of an armature of an electronically controlled solenoid device. An electronically controlled solenoid device is provided having a first stator and a first coil operatively associated with the first stator, a second stator and a second coil operatively associated with the second stator, and an armature mounted for movement between the first and second stators. The armature defines a magnetic circuit with each of the first and second stators and their associated coils. A flux, of a magnetic circuit associated with each coil is ramped in a generally linear manner over a period of time. A nominal position of the armature is defined where current in both of the coils is substantially equal. A current slope of each of the coils resulting from the associated ramped flux is observed. An offset of each current slope from the current slope of the nominal position is indicative of the static position of the armature.
In accordance with another aspect of the invention, a method of is provided for adjusting a position of an armature of an electronically controlled solenoid device. An electronically controlled solenoid device is provided having a first stator and a first coil operatively associated with the first stator, a second stator and a second coil operatively associated with the second stator, and an armature mounted for movement between the first and second stators. The armature defines a magnetic circuit with each of the first and second stators and their associated coils. A flux of a magnetic circuit associated with each coil is ramped in a generally linear manner over a period of time. A current slope of each of the coils resulting from the associated ramped flux is observed. A substantially identical thereby defining a magnetic center position of the armature.
Instead of ramping the flux and observing current as discussed above, current can be ramped and the rate of change of flux can a observed in accordance with the methods of the invention.
Other objects, features and characteristic of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification.